Hello Everyone.
Maxime did you try to put the apps COPS on the root of a new subdomain like https://cops.domain.tld/
i know it seems simple but maybe.
I just installed cops at the root of a new subdomain like https://cops.domain.tld/ and configured owncloud.
I have to install Calibre on a Desktop ( sorry i dont have any readers i don’t use eInk readers ihave only Books ) try to install a little database with calibre to synchronise with nextcloud and i will ask if it work.
Maybe you will try this before me.
But i ask you if it works tomorrow !!